LOCHINVAR TK-510CX3 1**

The figure of 209 therms is computed by this site, not published by the registry. It combines the registry's UEF, the ratio of hot water delivered to energy used, of 0.81 with the DOE test's daily hot-water draw for the high draw pattern. That draw pattern describes a larger household, or one where showers and laundry overlap. The registry also lists a maximum flow rate in gallons per minute of 5 for this unit. The energy source is DOE CCD, retrieved 2026-09-19. The figure holds only at the federal test's draw. A home that uses more or less hot water will use a different amount of gas, and this page has no value for that case. The method behind the annual cost is described on its own page.

Among the 397 models registered as a gas tankless unit at the high draw pattern, this one ranks 323rd lowest energy use of 397. Its 209 therms is 27 therms above the class median of 182 therms, which puts it in the highest quarter of its class for energy use. The flow rate of 5 may matter in a larger household, but the registry data does not show whether a given home needs it. A reader whose main concern is low gas use at this draw pattern may want to compare other models in the class. A same-class replacement can be found by model number, and the selector by fuel, space and size narrows the field further.

The running cost is not stated in the text because it depends on the average residential gas price in your state. The cost calculator takes your ZIP and applies that price to 209 therms. Any cost it returns applies only at the high draw pattern and the federal test's daily hot-water draw. The 27 therms gap to the class median of 182 therms scales with the same local price, so it changes the yearly cost by a similar proportion in any state. The modeled installed-cost range appears in its own block on the page with its source and date. It is a modeled range, not a quote, and it is not repeated here.